Control Of Underactuated Vehicles Research Articles

ESO-based path following control for underactuated vehicles with the safety prediction obstacle avoidance mechanism

This note investigates the waypoints-based path following problem of underactuated surface vehicles (USVs), considering that there exists the moving obstacle around the reference path. An improved dynamic virtual ship (DVS) guidance principle is proposed by incorporating the safety prediction obstacle avoidance (SPOA) strategy. In the mechanism, a real-time distance function is established to obtain the distance to closest point of approach (DCPA) and time to closest point of approach (TCPA), which are employed to evaluate the current sailing situation. Then the own ship could choose the corresponding sailing mode: path following mode or obstacle avoidance mode. Especially for the latter one, the velocity and the heading angle orders are taken into account together to generate the reasonable avoidance order, which is consistent with the International Regulations of Preventing Collisions at Sea (COLREGs) and the marine practice. Furthermore, based on the full-state observerable characteristic of the underactuated system, the ESO-based output feedback control algorithm is derived to guarantee the convergence of the own ship to the DVS. And the external disturbance and the model uncertainty are integrated as an augmented variable to be estimated. Besides, all signals in the closed-loop system are ensured to be semi-global uniformly ultimately bounded (SGUUB). The effectiveness and robustness of the proposed scheme are verified by the comparative experiment and the experiment within the simulated ocean environment.

Vision Restricted Path Planning and Control for Underactuated Vehicles

Autonomous vehicles can obtain navigation information by observing a source with a camera or an acoustic system mounted on the frame of the vehicle. This information properly fused provides navigation information that can overcome the lack of other sources of positioning. However, these systems often have a limited angular field-of-view (FOV). Due to this restriction, motion along some paths will make it impossible to obtain the necessary navigation information as the source is no longer in the vehicle’s FOV. This paper proposes both a path planning approach and a guidance control law that allows the vehicle to preserve a certain object or feature inside the FOV while at the same time converging to the proposed path.

Motion Primitives for Stabilization and Control of Underactuated Vehicles

In this paper we construct motion primitives as algorithm building blocks for stabilization and control of a class of underactuated systems that includes spacecraft, submersibles and planar vehicles. The underactuated systems are modelled as Lagrangian systems on Lie groups; thus, they are systems with drift and with accessibility distributions described by the operation of Lie bracket and symmetric product. Directions of motion that are not directly actuated are identified with symmetric products of the input vector fields, and in-phase sinusoidal forcing is used in the primitives to generate motion in these directions. These primitives can then be used for a variety of low velocity maneuvers. For example, we demonstrate their use for exponential point stabilization and for static interpolation. We evaluate our algorithms and investigate the advantage of planning motions along relative equilibria.